Since a liquid crystal display device is small and light, and consumes small electricity as compared to a Braun tube (cathode-ray tube), technologies of research, development, fabrication, and the like have rapidly made progress in recent years, and various liquid crystal display devices are commercialized and widely used.
FIG. 8 is a side view showing a liquid crystal display device LCD5 using a conventional lighting unit UT5, and FIG. 9 is an exploded perspective view of the lighting unit UT5. The conventional lighting unit UT5 comprises a fluorescent lamp 1 as a light source, a reflector 2 enclosing the fluorescent lamp 1 and configured to reflect light therefrom, a light guiding plate 3 disposed in the vicinity of the fluorescent lamp 1 for guiding the light therefrom, a reflecting sheet 4 disposed on a lower side of the light guiding plate 3 for reflecting the light, a housing 5 for holding these components from above and an outer peripheral side, and a rear surface cover 6 for holding the same from below. By disposing a liquid crystal display panel P on an emanating surface side of the lighting unit UT5, and by attaching a front side frame 8 or the like to the lighting unit UT5, the liquid crystal display device LCD5 is formed. In the liquid crystal display device LCD5 thus structured, a column-shaped light source unit storage space 103 is formed along a light-incident surface 3a of the light guiding plate 3 by means of the housing 5 and the rear surface cover 6, and a light source unit L to be described below is stored in the light source unit storage space 103. Reference numeral 102 denotes a clearance (exaggeratedly shown) formed between the reflector 2 and the housing 5. And, reference numeral 101 denotes another housing disposed so as to be opposed to the housing 5 for holding the light guiding plate 3 and the liquid crystal panel P.
The fluorescent lamp 1 as the light source is a fluorescent discharge tube such as a cold cathode tube. Rubber lamp holders 7, 7 are attached to both ends of the fluorescent lamp 1 and fixed to both ends of the reflector 2, and thereby the lamp 1 and the reflector 2 are integral with each other to form the light source unit L.
The light guiding plate 3 is a rectangular plate-shaped component made of transparent acrylic resin or the like for transmitting the light emitted from the fluorescent lamp 1 to an entire rear surface of the liquid crystal display panel P, and has the light-incident surface 3a corresponding to a side surface which the light from the fluorescent lamp 1 enters, two side surfaces 3b and 3c (not shown) both disposed adjacently to the light-incident surface 3a, an opposing light-incident surface 3d opposing to the light-incident surface 3a, an upper surface 3e, and a lower surface 3f. 
The reflecting sheet 4 is a rectangular sheet disposed along the lower surface 3f of the light guiding plate 3 for reflecting the light emanating from the light guiding plate 3 into the same again. One end 4a of the reflecting sheet 4 on the fluorescent lamp 1 side protrudes from the light guiding plate 3.
The reflector 2 is a sheet folded in U-shape in cross-section and has a high reflectivity. One end 2a of the reflector 2 on a lower side is disposed between the end 4a of the reflecting sheet 4 on the fluorescent lamp 1 side and the rear surface cover 6, for holding the end 4a of the reflecting sheet 4 on the fluorescent lamp 1 side from below by means of the end 2a of the reflector 2.
When the lighting unit UT5 thus structured is assembled, the light source unit L is incorporated (inserted) into the light source unit storage space 103 through an insertion opening E in the direction of insertion (direction indicated by arrow in FIG. 9) and disposed on a predetermined portion, in a state in which the light guiding plate 3 and the reflecting sheet 4 are disposed between the housing 5 and the rear surface cover 6.
In a case where the light source unit L is replaced due to a defect, break, or the like, the light source unit L is taken out of or inserted through the insertion opening E in the same manner. The end 2a of the reflector 2 is disposed between the reflecting sheet 4 and the rear surface cover 6, and the end 4a of the reflecting sheet 4 on the light source side protrudes from the light guiding plate 3 in order to inhibit an abnormal emission of light in the vicinity of the light source.
In the above-described liquid crystal display device LCD5, the light emanating from the fluorescent lamp 1 is collected by the reflector 2, and guided within the light guiding plate 3 while being reflected by the reflecting sheet 4, and, an entire rear surface of the liquid crystal display panel P is irradiated therewith. Thereby, characters and images are visually recognized.
However, in the lighting unit UT5 thus structured, when the lighting unit UT5 is assembled or the light source unit L is replaced, the end 4a of the reflecting sheet 4 protruding toward the fluorescent lamp 1 contacts the lamp holder 7 and is pressed down, by incorporating (inserting) the light source unit L through the insertion opening E. So, a clearance is generated between the light guiding plate 3 and the reflecting sheet 4, and the end 2a of the reflector 2 may enter the clearance in some cases. And, there has been a problem that, when such lighting unit UT5 is used in the liquid crystal display device LCD5, a display portion corresponding to the end 2a of the reflector 2 is brighter than other display portions and display quality is deteriorated. Therefore, when using the conventional lighting unit UT5, it has been impossible to stably obtain a liquid crystal display device with high display quality. And, when the end 2a of the reflector 2 enters the clearance between the light guiding plate 3 and the reflecting sheet 4, there has been no means to confirm and inspect this, and a problem that the reflecting sheet 4 may come off downwardly (toward rear surface cover 6) has occurred.